John J. Cannell, M.D writes that he receives numerous questions from individuals who ask, “My doctor prescribed Drisdol, is that OK?”

Drisdol is vitamin D2 in a form that doctors write prescriptions for. Sun exposure does not produce vitamin D2 in the body, the vitamin is produced by plant matter and irradiating fungus. When consumed, numerous metabolic forms of D2 can be traced in the body. According to some studies, vitamin D3, which is produced by the skin, is more powerful, hence more effective at raising blood levels compared with vitamin D2, however, some studies say they are equal. Few studies however have compared the efficiency of D2 versus D3, or, to put it simply, which form has better health outcomes and which better mortality rates?

Lead researcher, professor Dr. Goran Bjelakovic decided to investigate the question in a meta-analysis, which was followed by a recent review.

Bjelakovic evaluated 50 randomized controlled trials (RCTs) that included a total of 94,000 participants who took some form of vitamin D. Mortailty rates were reported as either primary of secondary outcomes. Whilst 74,000 participants in 32 trials used D3, the remaining 18,000 participants in the other 12 trials took D2. He discovered that the relative risk increased by 2% for participants in the vitamin D2-group, whilst those in the D3-group had a relative risk reduction of 6%.

Incredibly, the study was somehow overlooked and neither the press nor Cannell spotted it in July. Thanks to a recent review of the study by Professor Dr. Harvey Murff of Vanderbilt University in the Annals of Internal Medicine, the general public is now able to examine the study once again.

Cannell says:

“You would think a paper that took a look at tens of thousands of subjects and analyzed the efficacy of prescription vitamin D (D2) and over-the-counter vitamin D (D3) would warrant a news story or two. To my knowledge, these papers are the first to paint such a clear picture about the efficacy between D3 and D2. While there may be explanations for D3’s superiority other than improved efficacy, for the time being, these papers send doctors a message: use D3, not D2.”

Written by Grace Rattue